Axelark III with a summoned blade below him.
Axelark III is a boss that was added in update 1.6. He is summoned by using the Spirit Gem while outside of shops and safe zones. He has no direct ranged attacks. Instead, he summons three spinning blades that deal 7 damage on contact and follow him. He alternates between chasing the nearest player and stopping, much like other boss enemies. He has 4000 health while the spinning blades that follow him cannot be damaged or killed. They will stop chasing the player when Axelark III dies, but they will continue to spin.Upon defeating him, you will get the Spirit race.
Possibly a reference from Axelark IV in Roguelands, another game of the creator.